What is the difference between self and yourself in Smalltalk?

Question

In Smalltalk, there are two terms often found within a method body: self and yourself.

What is the difference between them?

Answer 1

self is a synonym for an object: specifically the receiver of the message that invoked the method. It is used within the body of a method.

yourself is a message that you can send to an object, that returns the receiver of the message.

anObject yourself returns anObject.

yourself is often used at the end of a message cascade within a method body.

When you want the return value from the method to be the receiver, but the final message in the cascade returns something else, you could write either:

self aMessageReturningTheReceiver;
      aMessageReturningTheArgument: anArgument .
^self

or

self aMessageReturningTheReceiver;
      aMessageReturningTheArgument: anArgument;
      yourself